Signaling and control channel structures for multiple services

ABSTRACT

Methods and systems are provided to allow signals for multiple service slices using sub-bands that are part of a system bandwidth. In some cases the signals for a given service slice are self-contained within the sub-band in the sense that channels for initial access and ongoing communications are all located within the sub-band. A receiver that is only accessing the given service slice need only be capable of receiving the sub-band. The method may involve, in a first sub-band predefined for a first service slice, transmitting first initial access information for a first service associated with the first service slice. The method further involves, in a second sub-band predefined for a second service slice, transmitting second initial access information for a second service associated with the second service slice. The second sub-band is different from the first sub-band.

CROSS REFERENCE

This application is a continuation of U.S. patent application Ser. No.15/015,649, filed Feb. 4, 2016, entitled “Signaling and Control ChannelStructures for Multiple Services”, now U.S. Pat. No. 10,405,300, thecontents of which are incorporated by reference herein in theirentirety.

FIELD

The application relates to signaling and control channel structures formultiple services.

BACKGROUND

Multiple services that are available within a single network may havedramatically different bandwidth requirements. Examples include machinetype communications (MTC) which have a relatively small bandwidthrequirement within an overall system bandwidth and enhanced MobileBroadband (eMBB) which has a relatively large bandwidth requirementwithin the system bandwidth.

There is a general need for efficient bandwidth usage. In addition, itwould be desirable for MTC devices to be as low-cost as possible.Current Long Term Evolution (LTE) systems consist of signaling andcontrol channel structures in which different services are supportedwith the same signaling and control channel structures in the samebandwidth. Introducing a new service can only be supported by the samestructure, which may not be sufficiently flexible to accommodate thedifferent bandwidth and coverage requirements of the new service.

SUMMARY

According to one aspect of the present invention, there is provided amethod comprising: transmitting, in a first logical frequency resource,first data and first signaling information associated with the firstdata, the first signaling information including initial accessinformation associated with the first data; and transmitting, in asecond logical frequency resource, second signaling informationassociated with second data.

According to another aspect of the present invention, there is provideda method in a user equipment comprising: performing initial systemaccess using a first frequency sub-band; receiving an assignment ofresources to use for ongoing communications in a second sub-band; andperforming ongoing communications using the second sub-band, includingsubsequent access.

According to a further aspect of the present invention, there isprovided an apparatus comprising: a first transmitter configured totransmit, in a first logical frequency resource, first data and firstsignaling information associated with the first data, the firstsignaling information including initial access information associatedwith the first data; and a second transmitter configured to transmit, ina second logical frequency resource, second signaling informationassociated with second data.

According to still another aspect of the present invention, there isprovided an apparatus comprising: a transmitter configured to provide afirst service by transmitting, in a first logical frequency resource,first data and first signaling information associated with the firstdata, the first signaling information including initial accessinformation associated with the first data; and the transmitter furtherconfigured to transmit, in a second logical frequency resource, secondsignaling information associated with second data.

According to one aspect of the present disclosure, there is provided amethod comprising: in a first sub-band predefined for a first serviceslice, transmitting first initial access information for a first serviceassociated with the first service slice; and in a second sub-bandpredefined for a second service slice, transmitting second initialaccess information for a second service associated with the secondservice slice, the second sub-band being different from the firstsub-band.

Optionally, the first initial access information includes a firstsynchronization channel and a first broadcast channel; and the secondinitial access information includes a second synchronization channel anda second broadcast channel.

Optionally, the first synchronization channel and the first broadcastchannel have a different periodicity than the second synchronizationchannel and the second broadcast channel.

Optionally, the method further comprises: transmitting, in the firstsub-band, an indication of a third sub-band to use for ongoingcommunications, the third sub-band being different from the first andsecond sub-bands.

Optionally, the third sub-band is also used for subsequent access.

Optionally, the first initial access information includes a firstacknowledgement (ACK)/negative acknowledgement (NACK) channel; and thesecond initial access information includes a second ACK/NACK channel.

Optionally, the first initial access information includes a first randomaccess channel; and the second initial access information includes asecond random access channel.

Optionally, the first sub-band has a first subcarrier spacing, and thesecond sub-band has a second subcarrier spacing different from the firstsubcarrier spacing.

Optionally, the first sub-band is a logical sub-band, and the secondsub-band is a logical sub-band.

Optionally, the method further comprises: using a first hypercellidentifier (ID) for transmissions in the first sub-band; and using asecond hypercell ID for transmissions in the second sub-band, the secondhypercell ID being different from the first hypercell ID.

According to another aspect of the present disclosure, there is providedan apparatus comprising at least one transmitter configured to: in afirst sub-band predefined for a first service slice, transmitting firstinitial access information for a first service associated with the firstservice slice; and in a second sub-band predefined for a second serviceslice, transmitting second initial access information for a secondservice associated with the second service slice, the second sub-bandbeing different from the first sub-band.

Optionally, the at least one transmitter comprises a single transmitterthat transmits both the first initial access information and the secondinitial access information.

Optionally, the at least one transmitter comprises a first transmitterthat transmits the first initial access information and a secondtransmitter that transmits the second initial access information.

Optionally, the first initial access information includes a firstsynchronization channel and a first broadcast channel; and the secondinitial access information includes a second synchronization channel anda second broadcast channel.

Optionally, the first synchronization channel and the first broadcastchannel have a different periodicity than the second synchronizationchannel and the second broadcast channel.

Optionally, the apparatus as described above, wherein the at least onetransmitter is further configured to: transmit, in the first sub-band,an indication of a third sub-band to use for ongoing communications, thethird sub-band being different from the first and second sub-bands.

Optionally, the third sub-band is also used for subsequent access.

Optionally, the first initial access information includes a firstacknowledgement (ACK)/negative acknowledgement (NACK) channel; and thesecond initial access information includes a second ACK/NACK channel.

Optionally, the first initial access information includes a first randomaccess channel; and the second initial access information includes asecond random access channel.

Optionally, the first sub-band has a first subcarrier spacing, and thesecond sub-band has a second subcarrier spacing different from the firstsubcarrier spacing.

Optionally, the first sub-band is a logical sub-band, and the secondsub-band is a logical sub-band.

Optionally, the at least one transmitter is further configured to: use afirst hypercell identifier (ID) for transmissions in the first sub-band;and use a second hypercell ID for transmissions in the second sub-band,the second hypercell ID being different from the first hypercell ID.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure will now be described with reference tothe attached drawings in which:

FIG. 1 is an example of a time frequency resource allocation diagramshowing allocation of resources for multiple services;

FIG. 2A is a system diagram showing different hypercell IDs fordifferent services;

FIG. 2B is a system diagram showing a single hypercell ID providingdifferent services;

FIG. 3A is an example of logical partitioning and service dependentmapping;

FIG. 3B is another example of logical partitioning and service dependentmapping;

FIG. 4 is an example of coexistence of a default frame structure and MTCframe structure within a narrow sub-band;

FIG. 5 is an example of a default frame structure and a nearbyself-contained MTC frame structure;

FIG. 6A is a block diagram of a transmitter for transmitting multipleservice slices; and

FIG. 6B is a block diagram of a receiver for receiving a service slice.

DETAILED DESCRIPTION

A Software Configurable Air Interface (SoftAI) has been proposed toaddress diverse services and device capabilities. See for example USpublication no. US20140016570 entitled “System and Method forDynamically Configurable Air Interface”, hereby incorporated byreference in its entirety. A default frame structure may be defined tofacilitate user equipment (UE) initial access and to instruct a UE touse frame structure configurations in other sub-bands. A default framestructure may be used for initial access to various services, and neednot be service-specific. In such a situation, the UE would need to beable to receive both the sub-band containing the default framestructure, and the sub-band containing the instructed frame structure.

It would be desirable for MTC devices to be low cost devices, which mayrequire that these devices only support narrowband transmission andreception. For a very wide system bandwidth (e.g. 100 MHz), it may notbe feasible to make a low cost MTC device that supports simultaneouslymultiple sub-bands for default frame structure (for control signaling)and machine type communications (for data exchange).

In some embodiments, a system bandwidth is configured with a respectivesub-band for each service. For at least one of the services, aself-contained set of signaling and data channels can be defined withinthe configured sub-band such that a UE obtaining that service need onlymonitor the configured sub-band instead of the entire system bandwidth.

Referring now to FIG. 1, shown is a first example in which a systembandwidth, which might for example be 20 MHz or wider, is divided into afirst sub-band 100 and a second sub-band 101. The system bandwidth is abandwidth associated with a system operating on a same carrierfrequency. There may be a larger number of sub-bands. Differingnumerologies and/or channelizations may be employed within the twosub-bands See for example commonly assigned co-pending U.S. provisionalapplication No. 62/169,342 to Liqing Zhang et al., entitled “System andScheme of Scalable OFDM Numerology”, U.S. application Ser. No.14/942,983 entitled “Resource Block Channelization for OFDM-basednumerologies”, and U.S. application Ser. No. 15/006,772 entitled “Systemand Method for Bandwidth Division and Resource Block Allocation”, all ofwhich are hereby incorporate by reference in their entirety.

A respective service slice is implemented within each sub-band 100,101.For the purpose of this example, an eMBB service is implemented withinsub-band 100, and an MTC service is implemented within sub-band 101, butmore generally, in some embodiments, two or more different services areprovided within two or more corresponding sub-bands. The sub-bandlocation, frame structure configuration, and bandwidth can be predefinedfor each service slice. In the illustrated example, the transmissionresources are for downlink transmissions. More generally, the methodsand systems described herein can be applied to downlink, or uplink, orboth downlink and uplink depending on the application. Downlinktransmissions on multiple sub-bands, such as sub-band 100 and sub-band101, may be from the same or different network elements.

The first sub-band 100 is allocated for an air interface configurationincluding transmission resources for data, and signalling informationassociated with the data. In the illustrated example, the data andsignalling information are associated with a first service, which may beeMBB. A default frame structure 109 for initial access is defined withinsub-band 100.

The default frame structure 109 includes a default synchronizationchannel 106, and a default broadcast channel 108. The default framestructure repeats on an ongoing basis, for example every 10 ms. Moregenerally, a default structure with differently allocated resourcesand/or periodicity may be provided. The default frame structure may alsoinclude a random access channel (not shown). Channels that are neededfor initial access are included in the default frame structure. In theillustrated example, these include the default synchronization channel106 for obtaining the timing of the orthogonal frequency divisionmultiplexing (OFDM) symbols and frame, and the default broadcast channel108 carrying basic system information. Remaining space within thedefault frame structure can be used to carry data.

Other channels that are not necessary for initial access may not need tobe inside the default frame structure 109. In the illustrated example,such additional channels include a control channel for eMBB 104 whichmay be partly inside the default frame structure 109 and partly outsidethe default frame structure 109; and an acknowledgement/negativeacknowledgement (ACK/NACK) channel 110.

In operation, with the default frame structure 109, initial access foreMBB service can be performed using the channels provided by the defaultframe structure. The default frame structure can also be used to informthe UE of what resources to use for ongoing communications. For eMBB,this would involve allocating resources within sub-band 100.

The second sub-band 101 is allocated for an air interface configurationincluding transmission resources for data, and signalling informationfor MTC. Shown is a frame structure 120 that includes resources forinitial access including an MTC synchronization channel 111 and an MTCbroadcast channel 112. Synchronization for MTC might be performed every100 ms, for example. The frame structure 120 also includes otherresources for ongoing communication including an MTC ACK/NACK channel114, and MTC control channel 116. In some embodiments, sub-band 101 islocated at the edge of a given system bandwidth.

Within sub-band 101, the MTC synchronization channel 111 and thebroadcast channel 112 may be defined in accordance with an MTC framestructure, different from the default frame structure 109. Channels 111and 112 may have a different periodicity and/or different resourcemapping (e.g. mapped over time) than channels 106 and 108. For example,the MTC synchronization channel 111 may have a longer periodicity thanthe default synchronization channel 106 due to low mobility of MTCdevices. The MTC broadcast channel 112 may have longer periodicity thanthe default broadcast channel 108 due to less change in systeminformation. In operation, MTC UEs tune to the pre-defined MTC framestructure configuration for synchronization and system information.

In the example, above, a different service is implemented within each ofsub-bands 100,101. In another embodiment, the same service isimplemented within each of two or more sub-bands, each of which containsall the resources necessary for end to end communications in thatsub-band, including both those necessary for initial access and thosenecessary for ongoing communications. In a specific embodiment, an MTCservice is provided within each of two sub-bands which may be contiguousor not. This would be suitable in a situation where there is a largeamount of MTC traffic that might not fit within a single sub-band. Byproviding two sub-bands that each provide resources for both initialaccess and ongoing communication, a UE will not need to rely onout-of-band control channel for initial access. In some embodiments,where there are two sub-bands that provide a given service, for exampleMTC, the sub-band assigned to a given UE may be predefined. Anotherexample will now be described again with reference to FIG. 1. In thisexample, a system bandwidth is divided into sub-band 101 for a firstservice which is the same as described in the previous example, andsub-band 103 for a second service. Sub-band 103 is further subdividedinto sub-band 100 which is the same as described in the previousexample, and another sub-band 102. The two sub-bands 100,102 might, forexample, be used to support two differing numerologies for the sameservice, for example eMBB. In another example, the two sub-bands 100,102 might be used to support two differing numerology options for twodifferent services, for example eMBB and broadcast services. The twosub-bands 100,102 can share common control channels. For example,control channel 104 can be used to provide control information such asresource assignment for sub-bands 100 and 102. In some embodiments,where multiple sub-bands are provided for a single service, such assub-band 100 and 102, a default frame structure can be used to informthe user of what resources to use for ongoing communications within themultiple sub-bands provided for the service. For example, a UE thatperforms initial access using the default frame structure 109 onsub-band 100 can be informed of, and instructed to use, resources withinsub-band 100 or sub-band 102 for on-going communications. Note that theUE in this scenario needs to be able to receive and decode sub-band 103.In some embodiments, where a UE is instructed to use a differentsub-band for ongoing communications than was used for initial access,the UE also uses the different sub-band for subsequent access. In someembodiments, the size of sub-bands 100, 101, 102 can be adjusted by thenetwork over time. The adjustment can be based on the availablebandwidth of the system, traffic loading of different services on thedifferent sub-bands and/or the number of UEs supported on the differentsub-bands. In addition, the signaling and control channel structures maydiffer in the case of varying the sub-band bandwidth.

In some embodiments, channel structures are implemented to supportdifferent coverage requirements of different services. For example, eMBBcontrol channels may have different coverage requirements than MTCcontrol channels. For example, MTC control channels may need to reachdevices in basements, and may not have to accommodate device mobility.

Each UE is responsible for processing received signals within a specificsub-band. From the network perspective, the sub-bands are notnecessarily dedicated to the specific services. Resources that are leftover after all the required channels are accounted for can be allocatedto other purposes.

In some embodiments, the data and control channels of different servicesmay be covered by different hypercell IDs. An example is depicted inFIG. 2A, where a system bandwidth is divided into a first sub-band 200for a first service slice (Service Slice #1), for example eMBB, and asecond sub-band 202 for a second service slice (Service Slice #2), forexample MTC. A first hypercell (Hypercell #1, more generally a firstlogical entity) 204 is composed of network elements206,208,210,212,214,216 operating on the first service slice, and asecond hypercell (Hypercell #2, more generally a second logical entity)218 is composed of network elements 214,220,222 operating on the secondservice slice. A network element can be a base station, an access pointor a remote radio head (RRH) connected to a network controller, forexample. It can be seen that network element 214 is operating on bothservice slices. In this case, the transmitter of network element 214transmits signaling information for both Service Slice #1 200 andService Slice #2 202. Network elements 206, 208, 210, 212, 216 transmitsignaling information for Service Slice #1 200. Network elements 220,222 transmit signaling information for Service Slice #2 202. FIG. 2Bdepicts another example in which Service Slice#1 and Service Slice#2 areboth provided by a single Hypercell 230.

In some embodiments, a logical to physical frequency partition mappingis configurable based on service scenarios and device capabilities. Forexample, a first service such as a low cost MTC service may have adirect logical to physical mapping within a physically confinedsub-band, and a second service such as eMBB may use a hopping pattern tomap logic resources to physical resources.

An example is depicted in FIG. 3A, where a logical partitioning for twoservice slices is depicted at 300. The frequency axis of the left sideof FIG. 3 represents a logical frequency resources. A partition 302 isallocated for a first service slice, and a partition 304 is allocatedfor a second service slice. A service dependent mapping is employed,such that the partition 302 is mapped at 305 to resources 306 using ahopping pattern, and partition 304 is mapped at 307 directly to aconfined sub-band 308. It is noted that the two mappings 305,307 depicttwo different mapping options for mapping a block of logical frequencyto physical resources. Another example is depicted in FIG. 3B whichshows a combination of direct mapping 314 for a sub-band 310 to physicalresource 320, and a mapping 314 using a hopping pattern for a sub-band312 to a physical resource 320.

Another example is depicted in FIG. 4 which shows a default framestructure defined within a sub-band 400 of an overall system bandwidth.In this example, a frame structure 404 for MTC occurs within the samesub-band as the default frame structure 402 in a time divisionmultiplexed (TDM) fashion. Advantageously, with such a structure, an MTCdevice can perform initial access using the default frame structure, andperform on-going communications with the MTC frame structure, and onlyneeds to monitor one sub-band. This allows lower-cost MTC devices to bebuilt that do not need the capability of hopping between sub-bands.

Another example is depicted in FIG. 5. In this example, there is a firstsub-band 500 containing a pre-defined default frame structure 504. Thereis a second sub-band 502 which is a self-contained frame structure 506for MTC, and containing, for example, MTC sync and broadcast channelconfigured for MTC. In operation, a UE tunes to the pre-defined defaultframe structure 504 for initial synchronization and system informationof MTC configurations (e.g. the sub-band for machine type services).This is only for initial access to the system or a change in the MTCsub-band location. In this example, the two sub-bands 500,502 arecollectively confined to a physical bandwidth (not shown) such that theUE does not need to support a large bandwidth.

In subsequent network entry, a UE immediately performs initial access inthe MTC sub-band 502. MTC synchronization and related system informationis carried in the sub-band for machine type services, and as such,sub-band 502 is self-contained for MTC operation.

In embodiments in which it is desirable to minimize the receptioncapabilities of an MTC device, the self-contained MTC frame structure islocated close to the default frame structure in frequency.

In an example method of MTC UE initial access, a MTC UE searchespotential carrier frequencies (Radio Frequency (RF) channels) in thesupported bands. Each carrier frequency may, for example, be identifiedby an E-UTRA Absolute Radio Frequency Channel Number (EARFCN). Thenumber of carrier frequencies of each band maybe a reduced set from afull set in a spectrum band. For each potential carrier frequency, theMTC UE tries to acquire synchronization by detecting the synchronizationchannel. In some embodiments, an MTC UE tries a MTC-specific syncchannel and a regular sync channel.

Referring now to FIG. 6A, shown is an example simplified block diagramof part of a transmitter that can be used to transmit channels for oneor more services in a self-contained manner. In this example, there areL services, each with a respective numerology, where L>=2, but moregenerally, it is not necessary that a different numerology be used foreach service.

For each service, there is a respective transmit chain 600,602. FIG. 6Ashows simplified functionality for the first and Lth numerology; thefunctionality for other numerologies would be similar. In the case wheretransmissions for the different services are from differing networkelements, transmit chain 600 would be in a first network element andtransmit chain 602 would be in a second network element. Also shown inFIG. 6B is simplified functionality for a receive chain 603 for areceiver operating using the first numerology.

The transmit chain 600 for the first numerology includes a constellationmapper 610, subcarrier mapper and grouper 611, IFFT 612 with subcarrierspacing SC₁, pilot symbol (P/S) and cyclic prefix inserter 614, andspectrum shaping filter 616. In operation, constellation mapper 610receives user content containing data and/or signalling 618 for K₁ UEs,where K₁>=1. In the case of self-contained data and signaling in asub-band, the signaling information including initial access informationfor a service is included as part of user content 618. In the case ofinitial access being performed within a first logical frequencyresource, and ongoing communications being performed within a secondlogical resource, user content 618 for transmit chain 600 will containthe signaling information for initial access, and user content foranother transmit chain (e.g. user content 630 for transmit chain 602)contains content for ongoing communications.

The constellation mapper 610 maps data and signalling information forthe first service to a respective stream of constellation symbols andoutputs the streams of constellation symbols 620. The number of bits persymbol depends on the particular constellation employed by theconstellation mapper 610. In the example of 4-quadrature amplitudemodulation (4-QAM), 2 bits from for each user are mapped to a respectiveQAM symbol.

For each OFDM symbol period, the subcarrier mapper and grouper 611groups and maps the constellation symbols produced by the constellationmapper 610 to up to P inputs of the IFFT 612 at 622. The grouping andmapping is performed based on scheduler information, which in turn isbased on channelization and resource block assignment, in accordancewith a defined resource block definition and allocation for the contentof the K₁ UEs being processed in transmit chain 600. P is the size ofthe IFFT 612. Not all of the P inputs are necessarily used for each OFDMsymbol period. The IFFT 612 receives up to P symbols, and outputs P timedomain samples at 624. Following this, in some implementations, timedomain pilot symbols are inserted and a cyclic prefix is added in block614. The spectrum shaping filter 616 applies a filter f₁(n) which limitsthe spectrum at the output of the transmit chain 600 to mitigateinterference with the outputs of other transmit chains such as transmitchain 602. The spectrum shaping filter 616 also performs shifting ofeach sub-band to its assigned frequency location.

The functionality of the other transmit chains, such as transmit chain602, is similar. The outputs of all of the transmit chains are combinedin a combiner 604 before transmission on the channel.

FIG. 6B shows a simplified block diagram of a receive chain for a UEoperating with the first numerology depicted at 603. In someembodiments, a given user equipment supports only one service (e.g. MTC)and is permanently configured to operate with a particular numerology.In some embodiments, a given UE operates with a configurable numerology.The receive chain 603 includes spectrum shaping filter 630, cyclicprefix deleter and pilot symbol processer 632, fast Fourier transform(FFT) 634, subcarrier de-mapper 636 and equalizer 638. Each element inthe receive chain performs corresponding reverse operations to thoseperformed in the transmit chain. The receive chain for a UE operatingwith another numerology would be similar.

In some embodiments, a system bandwidth is configured with a respectivesub-band for each service, and at least one sub-band is reserved forfuture use. A self-contained set of signaling and data channels can bedefined within the reserved sub-band completely independently of theexisting sub-bands, and without interfering with the existing sub-bands.This provides a measure of future proofing.

In some embodiments, as described above, multiple different numerologiesare used. These may differ across sub-bands, with a different numerologybeing used for each service slice. In some embodiments, multiplenumerologies are used for one service. Frame structures have beenproposed that are flexible in terms of the use of differingnumerologies. A numerology is defined in terms of subcarrier spacing andof OFDM symbol duration, and may also be defined by other parameterssuch as inverse fast Fourier transform (IFFT) length, transmit timeinterval (TTI) length, and cyclic prefix (CP) length or duration. Thesenumerologies may be scalable in the sense that subcarrier spacings aremultiples of each other as between the differing numerologies, and TTIlengths are also multiples of each other as between differingnumerologies. Such a scalable design across multiple numerologiesprovides implementation benefits, for example scalable total OFDM symbolduration in a time division duplex (TDD) context. See also Applicant'sco-pending U.S. provisional application No. 62/169,342 to Liqing Zhanget al., entitled “System and Scheme of Scalable OFDM Numerology”, herebyincorporated by reference in its entirety, which provides systems andmethods with scalable numerologies.

Table 1 below contains an example of a flexible frame structure designwith scalable numerologies in the four columns under “Frame structure”.Frames can be built using one or a combination of the four scalablenumerologies. For comparison purposes, in the right hand column of thetable, the conventional fixed LTE numerology is shown. In Table 1, eachnumerology uses a first cyclic prefix length for a first number of OFDMsymbols, and a second cyclic prefix length for a second number of OFDMsymbols. For example, in the first column under “Frame structure”, theTTI includes 3 symbols with a cyclic prefix length of 1.04 us followedby 4 symbols with a cyclic prefix length of 1.3 us.

The first column is for a numerology with 60 kHz subcarrier spacingwhich also has the shortest OFDM symbol duration. This may be suitablefor ultra-low latency communications, such as Vehicle-to-Any (V2X)communications, and more generally any industrial control application.The second column is for a numerology with 30 kHz subcarrier spacing.The third column is for a numerology with 15 kHz subcarrier spacing.This numerology has the same configuration as in LTE, except that thereare only 7 symbols in a TTI. This may be suitable for broadbandservices. The fourth column is for a numerology with 7.5 kHz spacing,which also has the longest OFDM symbol duration among the fournumerologies. This may be useful for coverage enhancement andbroadcasting. Of the four numerologies listed, those with 30 kHz and 60kHz subcarrier spacings are more robust to Doppler spreading (fastmoving conditions), because of the wider subcarrier spacing.

TABLE 1 Example set of Numerologies Parameters Frame structure Baseline(LTE) TTI Length 0.125 ms 0.25 ms 0.5 ms 1 ms TTI = 1 ms Subcarrier 60kHz 30 kHz 15 kHz 7.5 kHz 15 kHz spacing FFT size 512 1024 2048 40962048 Symbol 16.67 us 33.33 us 66.67 us 133.33 us 66.67 us duration#symbols 7 (3, 4) 7 (3, 4) 7 (3, 4) 7 (3, 4) 14 (2, 12) in each TTI CPlength 1.04 us, 1.30 us 2.08 us, 2.60 us 4.17 us, 5.21 us 8.33 us, 10.42us 5.2 us, 4.7 us (32, 40 point) (64, 80 point) (128, 160 point) (256,320 point) (160, 144 point) CP 6.67% 6.67% 6.67% 6.67% 6.67% overhead BW(MHz) 20 20 20 20 20

It should be understood that the specific numerologies of the example ofTable 1 are for illustration purposes, and that a flexible framestructure combining other numerologies can alternatively be employed.

OFDM-based signals can be employed to transmit a signal in whichmultiple numerologies coexist simultaneously. More specifically,multiple sub-band OFDM signals can be generated in parallel, each withina different sub-band, and each sub-band having a different subcarrierspacing (and more generally with a different numerology). The multiplesub-band signals are combined into a single signal for transmission, forexample for downlink transmissions. Alternatively, the multiple sub-bandsignals may be transmitted from separate transmitters, for example foruplink transmissions from multiple UEs. In a specific example, filteredOFDM (f-OFDM) can be employed. With f-OFDM, filtering is employed toshape the spectrum of each sub-band OFDM signal, and the sub-band OFDMsignals are then combined for transmission. f-OFDM lowers out-of-bandemission and improves transmission, and addresses the non-orthogonalityintroduced as a result of the use of different subcarrier spacings.

In some embodiments, the resource block definitions are configurable.For example, the number of tones per resource block can be varied acrosstime and/or system bandwidth. See for example Applicant's co-pendingU.S. application Ser. No. 14/952,983 filed Nov. 26, 2015, and entitled“Resource Block Channelization for OFDM-based Numerologies”, herebyincorporated by reference in its entirety.

Numerous modifications and variations of the present disclosure arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced otherwise than as specifically described herein.

We claim:
 1. A method comprising: in a first sub-band predefined for afirst service slice, transmitting first initial access information for afirst service associated with the first service slice; and in a secondsub-band predefined for a second service slice, transmitting secondinitial access information for a second service associated with thesecond service slice, the second sub-band being different from the firstsub-band.
 2. The method of claim 1, wherein: the first initial accessinformation includes a first synchronization channel and a firstbroadcast channel; and the second initial access information includes asecond synchronization channel and a second broadcast channel.
 3. Themethod of claim 2, wherein: the first synchronization channel and thefirst broadcast channel have a different periodicity than the secondsynchronization channel and the second broadcast channel.
 4. The methodof claim 2, further comprising: transmitting, in the first sub-band, anindication of a third sub-band to use for ongoing communications, thethird sub-band being different from the first and second sub-bands. 5.The method of claim 4, wherein the third sub-band is also used forsubsequent access.
 6. The method of claim 2, wherein: the first initialaccess information includes a first acknowledgement (ACK)/negativeacknowledgement (NACK) channel; and the second initial accessinformation includes a second ACK/NACK channel.
 7. The method of claim2, wherein: the first initial access information includes a first randomaccess channel; and the second initial access information includes asecond random access channel.
 8. The method of claim 1, wherein thefirst sub-band has a first subcarrier spacing, and the second sub-bandhas a second subcarrier spacing different from the first subcarrierspacing.
 9. The method of claim 1, wherein the first sub-band is alogical sub-band, and the second sub-band is a logical sub-band.
 10. Themethod of claim 1, further comprising: using a first hypercellidentifier (ID) for transmissions in the first sub-band; and using asecond hypercell ID for transmissions in the second sub-band, the secondhypercell ID being different from the first hypercell ID.
 11. Anapparatus comprising at least one transmitter configured to: in a firstsub-band predefined for a first service slice, transmit first initialaccess information for a first service associated with the first serviceslice; and in a second sub-band predefined for a second service slice,transmit second initial access information for a second serviceassociated with the second service slice, the second sub-band beingdifferent from the first sub-band.
 12. The apparatus of claim 11 whereinthe at least one transmitter comprises a single transmitter thattransmits both the first initial access information and the secondinitial access information.
 13. The apparatus of claim 11 wherein the atleast one transmitter comprises a first transmitter that transmits thefirst initial access information and a second transmitter that transmitsthe second initial access information.
 14. The apparatus of claim 11,wherein: the first initial access information includes a firstsynchronization channel and a first broadcast channel; and the secondinitial access information includes a second synchronization channel anda second broadcast channel.
 15. The apparatus of claim 14, wherein: thefirst synchronization channel and the first broadcast channel have adifferent periodicity than the second synchronization channel and thesecond broadcast channel.
 16. The apparatus of claim 14, wherein the atleast one transmitter is further configured to: transmit, in the firstsub-band, an indication of a third sub-band to use for ongoingcommunications, the third sub-band being different from the first andsecond sub-bands.
 17. The apparatus of claim 16, wherein the thirdsub-band is also used for subsequent access.
 18. The apparatus of claim14, wherein: the first initial access information includes a firstacknowledgement (ACK)/negative acknowledgement (NACK) channel; and thesecond initial access information includes a second ACK/NACK channel.19. The apparatus of claim 14, wherein: the first initial accessinformation includes a first random access channel; and the secondinitial access information includes a second random access channel. 20.The apparatus of claim 11, wherein the first sub-band has a firstsubcarrier spacing, and the second sub-band has a second subcarrierspacing different from the first subcarrier spacing.
 21. The apparatusof claim 11, wherein the first sub-band is a logical sub-band, and thesecond sub-band is a logical sub-band.
 22. The apparatus of claim 11,wherein the at least one transmitter is further configured to: use afirst hypercell identifier (ID) for transmissions in the first sub-band;and use a second hypercell ID for transmissions in the second sub-band,the second hypercell ID being different from the first hypercell ID.